The present invention relates to electrical systems controlled by motions of objects, for instance, electrical load switches, traffic lights, etc.
Various systems are already known in the prior art for detection of motion in a particular field of view. These systems include optical, ultrasonic, electromagnetic, and electrostatic, among other methods. All of these differ by the accuracy, reliability of detection, and cost of manufacture and installation. All of these systems are intended to detect motion and, determined by such detection of motion, to control appropriate electrical devices. However, up to the present time, no adequate equipment has been proposed for electrical switches. One of the reasons for this is the relatively complicated construction of known motion detectors, and a common purpose among all of these prior art systems is that they are used to detect the presence of motion.
U.S. Pat. No. 2,016,036, for example, disclosed a photoelectric system which utilized a grating disposed in front of each of two photoelectric cells so that the two photoelectric cells were affected differently by the motion of an object in the field of view, and hence, even though there was considerable ambient light, the motion of objects could be detected.
U.S. Pat. No. 2,142,378 utilized two photoelectric tubes with the light from a given field of view falling alternately on the two tubes by means of apertured light intercepting screens. By this means, the speed and direction of movement of an object could be determined.
U.S. Pat. No. 2,774,961 discloses a moving object indicator which utilizes two optical density wedges having continuous density gradations. Light from a field of view passes through these wedges to two separate photocells, which are connected in a bridge circuit. The bridge is normally balanced so that if there is no movement of the objects, there is no output from the moving object indicator. When a moving object is detected, this unbalances the bridge to provide an electrical output.
U.S. Pat. No. 3,972,021 discloses a field of view scanned by a pair of lenses and a beam splitter to illuminate a plurality of photoelectric detectors. The system detects the presence of motion within the field of view.
All of these known systems are relatively complicated, and are systems having a construction which detects the presence of motion of objects within the field of view.
The problem to be solved, therefore, is how to construct a system and the method of operation of a system which will determine when a person has left a room, thus de-energizing the lights in the room or some electrical appliance such as an electric soldering iron or an electric typewriter within the room.
Further, all known photodetectors and adjustable switches require a power supply independent of the power line to the load. This makes wiring more complicated and increases production and installation costs. The problem to be solved, therefore, includes how to establish a photodetector system which does not require any independent power supply.